Downlink calibration for a non-beamforming radio unit based on ue channel state information

Abstract

Apparatuses and methods in a communication system are disclosed. Antenna elements are used for transmitting, elements located in columns with two antennas per column. First transmission (422) having a reference signal utilises a first set of elements, while muting reference signals of other elements. Measurement report comprising first phase offset information regarding the first set of elements is received (426). A second transmission (430) having a reference signal utilises a second set of elements located in different columns while muting reference signals of the transmissions of other elements. Measurement report comprising second phase offset information regarding the second set of elements is received (432). Differentials are calculated between the phase offset informations and the phase offsets adjusted (434) of the transmissions to be similar by applying a phase shift correction based on the differentials.

1 . An apparatus in a communication system, comprising:
 a processor; and a memory including instructions, the instructions, when executed by the processor, cause the apparatus to:   control a given number of antenna elements for transmitting to a terminal device, the antenna elements being located in a given number of columns with two antennas per column;   select two antenna elements located in different columns as a first set of antenna elements;   transmit to the terminal device a first transmission utilising the first set of antenna elements, the transmission comprising a reference signal while muting reference signals of the transmissions of other antenna elements;   receive a measurement report from the terminal device, the measurement report comprising first phase offset information regarding the first set of antenna elements;   select two antenna elements of the given number of antenna elements located in different columns as a second set of antenna elements;   transmit to a terminal device a second transmission utilising the second set of antenna elements, the transmission comprising a reference signal while muting reference signals of the transmissions of other antenna elements;   receive a measurement report from the terminal device, the measurement report comprising second phase offset information regarding the second set of antenna elements;   calculate differentials between the obtained phase offset information and determine and adjust the phase offsets of the transmissions to be similar by applying a phase shift correction to an antenna of the second set of antenna elements based on the differentials;   perform the above transmitting, muting, receiving, calculating and adjusting the sets of antenna elements one at a time.   
     
     
         2 . The apparatus of  claim 1 , the memory and the computer program code configured to, with the processor, cause the apparatus further to:
 transmit to a terminal device a first transmission with first polarization utilising a first set of antenna elements and a second transmission with second polarization utilising a second set of antenna elements, each transmission comprising a reference signal;   calculate, after the muting, receiving and unmuting, phase differences of the first and second phase offset information and determine a phase shift correction based on the difference;   adjust the phase offsets of the transmissions to be similar by applying a phase shift correction to the first and second set of antenna elements.   
     
     
         3 . The apparatus of  claim 1 or 2 , the memory and the computer program code configured to, with the processor, cause the apparatus further to:
 perform the muting, receiving and adjusting at given time intervals.   
     
     
         4 . The apparatus of  any preceding claim , the memory and the computer program code configured to, with the processor, cause the apparatus further to:
 determine the differential of the first and second phase offset information with more than one terminal device;   determine the average differential of transmissions transmitted to different terminal devices;   determine an average phase shift correction based on the average differential and   adjust the phase offsets of the transmissions to be similar by applying the average phase shift correction.   
     
     
         5 . The apparatus of  any preceding claim , wherein the reference signals are terminal device specific. 
     
     
         6 . The apparatus of  claim 4 , wherein the reference signals are cell specific. 
     
     
         7 . The apparatus of  any preceding claim , wherein measurement report is a channel state information report, and the memory and the computer program code configured to, with the processor, cause the apparatus further to:
 utilise channel state information received from the terminal device before the muting operation in the transmission of beams to the terminal device during the muting operation.   
     
     
         8 . The apparatus of  any preceding claim , wherein the first and second sets of antenna elements are arranged corresponding to NR Type I Single panel codebook. 
     
     
         9 . The apparatus of  any preceding claim , wherein the terminal device is in line-of-sight and more than 10 m away from the first and second sets of antenna elements. 
     
     
         10 . A method in an apparatus in a communication system comprising the steps of:
 controlling a given number of antenna elements for transmitting to a terminal device, the antenna elements being located in a given number of columns with two antennas per column;   selecting two antenna elements located in different columns as a first set of antenna elements;   transmitting to the terminal device a first transmission utilising the first set of antenna elements, the transmission comprising a reference signal while muting reference signals of the transmissions of other antenna elements;   receiving a measurement report from the terminal device, the measurement report comprising first phase offset information regarding the first set of antenna elements;   selecting two antenna elements of the given number of antenna elements located in different columns as a second set of antenna elements;   transmit to a terminal device a second transmission utilising the second set of antenna elements, the transmission comprising a reference signal while muting reference signals of the transmissions of other antenna elements;   receiving a measurement report from the terminal device, the measurement report comprising second phase offset information regarding the second set of antenna elements;   calculating differentials between the obtained phase offset information and determine and adjust a phase shift correction of an antenna of the second set of antenna elements based on the differentials;   performing the above transmitting, muting, receiving, calculating and adjusting the sets of antenna elements one at a time.   
     
     
         11 . The method of  claim 10 , further comprising:
 transmitting to a terminal device a first transmission with first polarization utilising a first set of antenna elements and a second transmission with second polarization utilising a second set of antenna elements, each transmission comprising a reference signal;   calculating, after the muting, receiving and unmuting, phase differences of the first and second phase offset information and determine a phase shift correction based on the difference;   adjusting the phase offsets of the transmissions to be similar by applying a phase shift correction to the first and second set of antenna elements.   
     
     
         12 . The method of  claim 10 or 11 , further comprising:
 performing the muting, receiving and adjusting at given time intervals.   
     
     
         13 . The method of  any preceding claims 10 to 12  further comprising:
 determining the differential of the first and second phase offset information with more than one terminal device; 
 determining the average differential of transmissions transmitted to different terminal devices; 
 determining an average phase shift correction based on the average differential and 
 adjusting the phase offsets of the transmissions to be similar by applying the average phase shift correction. 
 
     
     
         14 . The method of  any preceding claims 10 to 13 , wherein the reference signals are terminal device specific. 
     
     
         15 . The method of  claim 13 , wherein the reference signals are cell specific. 
     
     
         16 . The method of  any preceding claims 10 to 15 , wherein measurement report is a channel state information report, and the memory and the computer program code configured to, with the processor, cause the apparatus further to:
 utilise channel state information received from the terminal device before the muting operation in the transmission of beams to the terminal device during the muting operation.   
     
     
         17 . The method of  any preceding claims 10 to 15 , wherein the first and second sets of antenna elements are arranged corresponding to NR Type I Single panel codebook. 
     
     
         18 . The method of  any preceding claims 10 to 16 , wherein the terminal device is in line-of-sight and more than 10 m away from the first and second sets of antenna elements. 
     
     
         19 . A computer program comprising instructions, which, when executed by an apparatus, cause the apparatus to perform at least the following:
 controlling a given number of antenna elements for transmitting to a terminal device, the antenna elements being located in a given number of columns with two antennas per column;   selecting two antenna elements located in different columns as a first set of antenna elements;   transmitting to the terminal device a first transmission utilising the first set of antenna elements, the transmission comprising a reference signal while muting reference signals of the transmissions of other antenna elements;   receiving a measurement report from the terminal device, the measurement report comprising first phase offset information regarding the first set of antenna elements;   selecting two antenna elements of the given number of antenna elements located in different columns as a second set of antenna elements; transmit to a terminal device a second transmission utilising the second set of antenna elements, the transmission comprising a reference signal while muting reference signals of the transmissions of other antenna elements;   receiving a measurement report from the terminal device, the measurement report comprising second phase offset information regarding the second set of antenna elements;   calculating differentials between the obtained phase offset information and determine and adjust a phase shift correction of an antenna of the second set of antenna elements based on the differentials;   performing the above transmitting, muting, receiving, calculating and adjusting the sets of antenna elements one at a time.